From 00fd4d2a4b7f17e40ae8fc7bc9ea01bbf07c3b78 Mon Sep 17 00:00:00 2001
From: andreaangiolillo <andrea.angiolillo@mongodb.com>
Date: Mon, 11 Mar 2024 13:47:11 +0000
Subject: [PATCH 1/6] Add mocking

---
 tools/cli/Makefile                            | 10 +-
 tools/cli/go.mod                              |  1 +
 tools/cli/go.sum                              |  2 +
 tools/cli/internal/cli/merge/merge.go         | 10 +-
 tools/cli/internal/cli/merge/merge_test.go    | 46 +++++++++
 tools/cli/internal/mocks/mock_openapi.go      | 93 +++++++++++++++++++
 .../openapi/errors/path_conflict_error.go     | 14 +++
 tools/cli/internal/openapi/oasdiff.go         | 56 +++--------
 tools/cli/internal/openapi/openapi.go         | 62 ++++++++++++-
 tools/cli/internal/openapi/openapi3.go        | 14 +++
 10 files changed, 259 insertions(+), 49 deletions(-)
 create mode 100644 tools/cli/internal/mocks/mock_openapi.go

diff --git a/tools/cli/Makefile b/tools/cli/Makefile
index 8dc6f04..8d7cdcd 100644
--- a/tools/cli/Makefile
+++ b/tools/cli/Makefile
@@ -24,6 +24,7 @@ deps:  ## Download go module dependencies
 .PHONY: devtools
 devtools:  ## Install dev tools
 	@echo "==> Installing dev tools..."
+	go install go.uber.org/mock/mockgen@latest
 	curl -sSfL https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh | sh -s -- -b $(shell go env GOPATH)/bin $(GOLANGCI_VERSION)
 
 .PHONY: setup
@@ -31,8 +32,8 @@ setup: deps devtools ## Set up dev env
 
 .PHONY: fmt
 fmt: ### Format all go files with goimports and gofmt
-	find . -name "*.go" -exec gofmt -w "{}" \;
-	find . -name "*.go" -exec goimports -l -w "{}" \;
+	find . -name "*.go" -not -path "./internal/mocks" -exec gofmt -w "{}" \;
+	find . -name "*.go" -not -path "./internal/mocks" -exec goimports -l -w "{}" \;
 
 .PHONY: build
 build:
@@ -57,6 +58,11 @@ fix-lint: ## Fix linting errors
 list: ## List all make targets
 	@${MAKE} -pRrn : -f $(MAKEFILE_LIST) 2>/dev/null | awk -v RS= -F: '/^# File/,/^# Finished Make data base/ {if ($$1 !~ "^[#.]") {print $$1}}' | egrep -v -e '^[^[:alnum:]]' -e '^$@$$' | sort
 
+.PHONY: gen-mocks
+gen-mocks: ## Generate mocks
+	@echo "==> Generating mocks"
+	rm -rf ./internal/mocks
+	go generate ./internal...
 
 .PHONY: help
 .DEFAULT_GOAL := help
diff --git a/tools/cli/go.mod b/tools/cli/go.mod
index 816185e..6b3adad 100644
--- a/tools/cli/go.mod
+++ b/tools/cli/go.mod
@@ -7,6 +7,7 @@ require (
 	github.com/spf13/cobra v1.8.0
 	github.com/stretchr/testify v1.9.0
 	github.com/tufin/oasdiff v1.10.11
+	go.uber.org/mock v0.4.0
 )
 
 require (
diff --git a/tools/cli/go.sum b/tools/cli/go.sum
index f98dcb9..acdc8f5 100644
--- a/tools/cli/go.sum
+++ b/tools/cli/go.sum
@@ -48,6 +48,8 @@ github.com/ugorji/go/codec v1.2.11 h1:BMaWp1Bb6fHwEtbplGBGJ498wD+LKlNSl25MjdZY4d
 github.com/ugorji/go/codec v1.2.11/go.mod h1:UNopzCgEMSXjBc6AOMqYvWC1ktqTAfzJZUZgYf6w6lg=
 github.com/yargevad/filepathx v1.0.0 h1:SYcT+N3tYGi+NvazubCNlvgIPbzAk7i7y2dwg3I5FYc=
 github.com/yargevad/filepathx v1.0.0/go.mod h1:BprfX/gpYNJHJfc35GjRRpVcwWXS89gGulUIU5tK3tA=
+go.uber.org/mock v0.4.0 h1:VcM4ZOtdbR4f6VXfiOpwpVJDL6lCReaZ6mw31wqh7KU=
+go.uber.org/mock v0.4.0/go.mod h1:a6FSlNadKUHUa9IP5Vyt1zh4fC7uAwxMutEAscFbkZc=
 golang.org/x/exp v0.0.0-20240119083558-1b970713d09a h1:Q8/wZp0KX97QFTc2ywcOE0YRjZPVIx+MXInMzdvQqcA=
 golang.org/x/exp v0.0.0-20240119083558-1b970713d09a/go.mod h1:idGWGoKP1toJGkd5/ig9ZLuPcZBC3ewk7SzmH0uou08=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
diff --git a/tools/cli/internal/cli/merge/merge.go b/tools/cli/internal/cli/merge/merge.go
index 2d849f9..b09ee2b 100644
--- a/tools/cli/internal/cli/merge/merge.go
+++ b/tools/cli/internal/cli/merge/merge.go
@@ -29,6 +29,10 @@ const (
 	DefaultOutputFileName = "FOAS.json"
 )
 
+// writeToFileFunc is a variable that holds the function used to write files.
+// It can be overridden in tests.
+var writeToFileFunc = os.WriteFile
+
 type Opts struct {
 	Merger        openapi.Merger
 	basePath      string
@@ -36,7 +40,7 @@ type Opts struct {
 	externalPaths []string
 }
 
-func (o *Opts) Run(_ []string) error {
+func (o *Opts) Run() error {
 	federated, err := o.Merger.MergeOpenAPISpecs(o.externalPaths)
 	if err != nil {
 		return err
@@ -65,7 +69,7 @@ func (o *Opts) PreRunE(_ []string) error {
 }
 
 func (o *Opts) saveFile(data []byte) error {
-	if err := os.WriteFile(o.outputPath, data, 0o600); err != nil {
+	if err := writeToFileFunc(o.outputPath, data, 0o600); err != nil {
 		return err
 	}
 
@@ -86,7 +90,7 @@ func Builder() *cobra.Command {
 			return opts.PreRunE(args)
 		},
 		RunE: func(_ *cobra.Command, args []string) error {
-			return opts.Run(args)
+			return opts.Run()
 		},
 	}
 
diff --git a/tools/cli/internal/cli/merge/merge_test.go b/tools/cli/internal/cli/merge/merge_test.go
index 856cfb6..3b30e03 100644
--- a/tools/cli/internal/cli/merge/merge_test.go
+++ b/tools/cli/internal/cli/merge/merge_test.go
@@ -15,12 +15,48 @@
 package merge
 
 import (
+	"os"
 	"testing"
 
+	"github.com/getkin/kin-openapi/openapi3"
+	"github.com/mongodb/openapi/tools/cli/internal/mocks"
+	"github.com/tufin/oasdiff/load"
+	"go.uber.org/mock/gomock"
+
 	"github.com/mongodb/openapi/tools/cli/internal/cli/flag"
 	"github.com/mongodb/openapi/tools/cli/internal/cli/validator"
 )
 
+func TestSuccessfulMerge_Run(t *testing.T) {
+	setupTest(t)
+	ctrl := gomock.NewController(t)
+	mockMergerStore := mocks.NewMockMerger(ctrl)
+
+	externalPaths := []string{"external.json"}
+	opts := &Opts{
+		Merger:        mockMergerStore,
+		basePath:      "base.json",
+		outputPath:    "foas.json",
+		externalPaths: externalPaths,
+	}
+
+	response := &load.SpecInfo{
+		Spec:    &openapi3.T{},
+		Url:     "test",
+		Version: "3.0.1",
+	}
+
+	mockMergerStore.
+		EXPECT().
+		MergeOpenAPISpecs(opts.externalPaths).
+		Return(response, nil).
+		Times(1)
+
+	if err := opts.Run(); err != nil {
+		t.Fatalf("Run() unexpected error: %v", err)
+	}
+}
+
 func TestCreateBuilder(t *testing.T) {
 	validator.ValidateSubCommandsAndFlags(
 		t,
@@ -29,3 +65,13 @@ func TestCreateBuilder(t *testing.T) {
 		[]string{flag.Base, flag.External, flag.Output},
 	)
 }
+
+func setupTest(t *testing.T) {
+	t.Helper()
+	writeToFileFunc = func(filename string, data []byte, perm os.FileMode) error {
+		return nil
+	}
+	defer func() {
+		writeToFileFunc = os.WriteFile
+	}()
+}
diff --git a/tools/cli/internal/mocks/mock_openapi.go b/tools/cli/internal/mocks/mock_openapi.go
new file mode 100644
index 0000000..464e1b1
--- /dev/null
+++ b/tools/cli/internal/mocks/mock_openapi.go
@@ -0,0 +1,93 @@
+// Code generated by MockGen. DO NOT EDIT.
+// Source: github.com/mongodb/openapi/tools/cli/internal/openapi (interfaces: Parser,Merger)
+//
+// Generated by this command:
+//
+//	mockgen -destination=../mocks/mock_openapi.go -package=mocks github.com/mongodb/openapi/tools/cli/internal/openapi Parser,Merger
+//
+
+// Package mocks is a generated GoMock package.
+package mocks
+
+import (
+	reflect "reflect"
+
+	load "github.com/tufin/oasdiff/load"
+	gomock "go.uber.org/mock/gomock"
+)
+
+// MockParser is a mock of Parser interface.
+type MockParser struct {
+	ctrl     *gomock.Controller
+	recorder *MockParserMockRecorder
+}
+
+// MockParserMockRecorder is the mock recorder for MockParser.
+type MockParserMockRecorder struct {
+	mock *MockParser
+}
+
+// NewMockParser creates a new mock instance.
+func NewMockParser(ctrl *gomock.Controller) *MockParser {
+	mock := &MockParser{ctrl: ctrl}
+	mock.recorder = &MockParserMockRecorder{mock}
+	return mock
+}
+
+// EXPECT returns an object that allows the caller to indicate expected use.
+func (m *MockParser) EXPECT() *MockParserMockRecorder {
+	return m.recorder
+}
+
+// CreateOpenAPISpecFromPath mocks base method.
+func (m *MockParser) CreateOpenAPISpecFromPath(arg0 string) (*load.SpecInfo, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "CreateOpenAPISpecFromPath", arg0)
+	ret0, _ := ret[0].(*load.SpecInfo)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// CreateOpenAPISpecFromPath indicates an expected call of CreateOpenAPISpecFromPath.
+func (mr *MockParserMockRecorder) CreateOpenAPISpecFromPath(arg0 any) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "CreateOpenAPISpecFromPath", reflect.TypeOf((*MockParser)(nil).CreateOpenAPISpecFromPath), arg0)
+}
+
+// MockMerger is a mock of Merger interface.
+type MockMerger struct {
+	ctrl     *gomock.Controller
+	recorder *MockMergerMockRecorder
+}
+
+// MockMergerMockRecorder is the mock recorder for MockMerger.
+type MockMergerMockRecorder struct {
+	mock *MockMerger
+}
+
+// NewMockMerger creates a new mock instance.
+func NewMockMerger(ctrl *gomock.Controller) *MockMerger {
+	mock := &MockMerger{ctrl: ctrl}
+	mock.recorder = &MockMergerMockRecorder{mock}
+	return mock
+}
+
+// EXPECT returns an object that allows the caller to indicate expected use.
+func (m *MockMerger) EXPECT() *MockMergerMockRecorder {
+	return m.recorder
+}
+
+// MergeOpenAPISpecs mocks base method.
+func (m *MockMerger) MergeOpenAPISpecs(arg0 []string) (*load.SpecInfo, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "MergeOpenAPISpecs", arg0)
+	ret0, _ := ret[0].(*load.SpecInfo)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// MergeOpenAPISpecs indicates an expected call of MergeOpenAPISpecs.
+func (mr *MockMergerMockRecorder) MergeOpenAPISpecs(arg0 any) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "MergeOpenAPISpecs", reflect.TypeOf((*MockMerger)(nil).MergeOpenAPISpecs), arg0)
+}
diff --git a/tools/cli/internal/openapi/errors/path_conflict_error.go b/tools/cli/internal/openapi/errors/path_conflict_error.go
index b01db5a..4493b51 100644
--- a/tools/cli/internal/openapi/errors/path_conflict_error.go
+++ b/tools/cli/internal/openapi/errors/path_conflict_error.go
@@ -1,3 +1,17 @@
+// Copyright 2024 MongoDB Inc
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 package errors
 
 import "fmt"
diff --git a/tools/cli/internal/openapi/oasdiff.go b/tools/cli/internal/openapi/oasdiff.go
index 54bf339..4ea4aa7 100644
--- a/tools/cli/internal/openapi/oasdiff.go
+++ b/tools/cli/internal/openapi/oasdiff.go
@@ -1,8 +1,20 @@
+// Copyright 2024 MongoDB Inc
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 package openapi
 
 import (
-	"log"
-
 	"github.com/mongodb/openapi/tools/cli/internal/openapi/errors"
 	"github.com/tufin/oasdiff/diff"
 	"github.com/tufin/oasdiff/load"
@@ -16,46 +28,6 @@ type OasDiff struct {
 	parser   Parser
 }
 
-func NewOasDiff(base string) (*OasDiff, error) {
-	parser := NewOpenAPI3()
-	baseSpec, err := parser.CreateOpenAPISpecFromPath(base)
-	if err != nil {
-		return nil, err
-	}
-
-	return &OasDiff{
-		base:   baseSpec,
-		parser: parser,
-		config: &diff.Config{
-			IncludePathParams: true,
-		},
-	}, nil
-}
-
-func (o *OasDiff) MergeOpenAPISpecs(paths []string) (*load.SpecInfo, error) {
-	for _, p := range paths {
-		spec, err := o.parser.CreateOpenAPISpecFromPath(p)
-		if err != nil {
-			return nil, err
-		}
-
-		specDiff, err := diff.Get(o.config, o.base.Spec, spec.Spec)
-		if err != nil {
-			log.Fatalf("error in calculating the diff of the specs: %s", err)
-			return nil, err
-		}
-
-		o.specDiff = specDiff
-		o.external = spec
-		err = o.mergeSpecIntoBase()
-		if err != nil {
-			return nil, err
-		}
-	}
-
-	return o.base, nil
-}
-
 func (o OasDiff) mergeSpecIntoBase() error {
 	return o.mergePaths()
 }
diff --git a/tools/cli/internal/openapi/openapi.go b/tools/cli/internal/openapi/openapi.go
index 5bdb959..555252f 100644
--- a/tools/cli/internal/openapi/openapi.go
+++ b/tools/cli/internal/openapi/openapi.go
@@ -1,13 +1,71 @@
+// Copyright 2024 MongoDB Inc
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 package openapi
 
+//go:generate mockgen -destination=../mocks/mock_openapi.go -package=mocks github.com/mongodb/openapi/tools/cli/internal/openapi Parser,Merger
 import (
+	"log"
+
+	"github.com/tufin/oasdiff/diff"
 	"github.com/tufin/oasdiff/load"
 )
 
+type Parser interface {
+	CreateOpenAPISpecFromPath(string) (*load.SpecInfo, error)
+}
+
 type Merger interface {
 	MergeOpenAPISpecs([]string) (*load.SpecInfo, error)
 }
 
-type Parser interface {
-	CreateOpenAPISpecFromPath(string) (*load.SpecInfo, error)
+func (o *OasDiff) MergeOpenAPISpecs(paths []string) (*load.SpecInfo, error) {
+	for _, p := range paths {
+		spec, err := o.parser.CreateOpenAPISpecFromPath(p)
+		if err != nil {
+			return nil, err
+		}
+
+		specDiff, err := diff.Get(o.config, o.base.Spec, spec.Spec)
+		if err != nil {
+			log.Fatalf("error in calculating the diff of the specs: %s", err)
+			return nil, err
+		}
+
+		o.specDiff = specDiff
+		o.external = spec
+		err = o.mergeSpecIntoBase()
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	return o.base, nil
+}
+
+func NewOasDiff(base string) (*OasDiff, error) {
+	parser := NewOpenAPI3()
+	baseSpec, err := parser.CreateOpenAPISpecFromPath(base)
+	if err != nil {
+		return nil, err
+	}
+
+	return &OasDiff{
+		base:   baseSpec,
+		parser: parser,
+		config: &diff.Config{
+			IncludePathParams: true,
+		},
+	}, nil
 }
diff --git a/tools/cli/internal/openapi/openapi3.go b/tools/cli/internal/openapi/openapi3.go
index 8e858f8..011386f 100644
--- a/tools/cli/internal/openapi/openapi3.go
+++ b/tools/cli/internal/openapi/openapi3.go
@@ -1,3 +1,17 @@
+// Copyright 2024 MongoDB Inc
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 package openapi
 
 import (

From 45ec0b18d1a913f209a85d437c9830bf35f98606 Mon Sep 17 00:00:00 2001
From: andreaangiolillo <andrea.angiolillo@mongodb.com>
Date: Mon, 11 Mar 2024 13:51:02 +0000
Subject: [PATCH 2/6] fixes

---
 tools/cli/internal/cli/merge/merge.go      |  2 +-
 tools/cli/internal/cli/merge/merge_test.go | 12 +++++-------
 2 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/tools/cli/internal/cli/merge/merge.go b/tools/cli/internal/cli/merge/merge.go
index b09ee2b..832cad7 100644
--- a/tools/cli/internal/cli/merge/merge.go
+++ b/tools/cli/internal/cli/merge/merge.go
@@ -89,7 +89,7 @@ func Builder() *cobra.Command {
 		PreRunE: func(_ *cobra.Command, args []string) error {
 			return opts.PreRunE(args)
 		},
-		RunE: func(_ *cobra.Command, args []string) error {
+		RunE: func(_ *cobra.Command, _ []string) error {
 			return opts.Run()
 		},
 	}
diff --git a/tools/cli/internal/cli/merge/merge_test.go b/tools/cli/internal/cli/merge/merge_test.go
index 3b30e03..2643084 100644
--- a/tools/cli/internal/cli/merge/merge_test.go
+++ b/tools/cli/internal/cli/merge/merge_test.go
@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+//go:build unit
+
 package merge
 
 import (
@@ -19,12 +21,11 @@ import (
 	"testing"
 
 	"github.com/getkin/kin-openapi/openapi3"
+	"github.com/mongodb/openapi/tools/cli/internal/cli/flag"
+	"github.com/mongodb/openapi/tools/cli/internal/cli/validator"
 	"github.com/mongodb/openapi/tools/cli/internal/mocks"
 	"github.com/tufin/oasdiff/load"
 	"go.uber.org/mock/gomock"
-
-	"github.com/mongodb/openapi/tools/cli/internal/cli/flag"
-	"github.com/mongodb/openapi/tools/cli/internal/cli/validator"
 )
 
 func TestSuccessfulMerge_Run(t *testing.T) {
@@ -68,10 +69,7 @@ func TestCreateBuilder(t *testing.T) {
 
 func setupTest(t *testing.T) {
 	t.Helper()
-	writeToFileFunc = func(filename string, data []byte, perm os.FileMode) error {
+	writeToFileFunc = func(_ string, _ []byte, _ os.FileMode) error {
 		return nil
 	}
-	defer func() {
-		writeToFileFunc = os.WriteFile
-	}()
 }

From 65b246d5b41103fe643976959ac8479c7069d9f0 Mon Sep 17 00:00:00 2001
From: andreaangiolillo <andrea.angiolillo@mongodb.com>
Date: Mon, 11 Mar 2024 14:09:45 +0000
Subject: [PATCH 3/6] Addressed PR comments - Part 1

---
 tools/cli/Makefile                               |  1 -
 tools/cli/internal/cli/merge/merge.go            |  6 +-----
 tools/cli/internal/cli/merge/merge_test.go       | 16 +++-------------
 .../internal/{mocks => openapi}/mock_openapi.go  |  6 +++---
 tools/cli/internal/openapi/openapi.go            |  2 +-
 5 files changed, 8 insertions(+), 23 deletions(-)
 rename tools/cli/internal/{mocks => openapi}/mock_openapi.go (93%)

diff --git a/tools/cli/Makefile b/tools/cli/Makefile
index 8d7cdcd..dfe6877 100644
--- a/tools/cli/Makefile
+++ b/tools/cli/Makefile
@@ -61,7 +61,6 @@ list: ## List all make targets
 .PHONY: gen-mocks
 gen-mocks: ## Generate mocks
 	@echo "==> Generating mocks"
-	rm -rf ./internal/mocks
 	go generate ./internal...
 
 .PHONY: help
diff --git a/tools/cli/internal/cli/merge/merge.go b/tools/cli/internal/cli/merge/merge.go
index 832cad7..d96ee0f 100644
--- a/tools/cli/internal/cli/merge/merge.go
+++ b/tools/cli/internal/cli/merge/merge.go
@@ -29,10 +29,6 @@ const (
 	DefaultOutputFileName = "FOAS.json"
 )
 
-// writeToFileFunc is a variable that holds the function used to write files.
-// It can be overridden in tests.
-var writeToFileFunc = os.WriteFile
-
 type Opts struct {
 	Merger        openapi.Merger
 	basePath      string
@@ -69,7 +65,7 @@ func (o *Opts) PreRunE(_ []string) error {
 }
 
 func (o *Opts) saveFile(data []byte) error {
-	if err := writeToFileFunc(o.outputPath, data, 0o600); err != nil {
+	if err := os.WriteFile(o.outputPath, data, 0o600); err != nil {
 		return err
 	}
 
diff --git a/tools/cli/internal/cli/merge/merge_test.go b/tools/cli/internal/cli/merge/merge_test.go
index 2643084..4b9db1f 100644
--- a/tools/cli/internal/cli/merge/merge_test.go
+++ b/tools/cli/internal/cli/merge/merge_test.go
@@ -12,26 +12,23 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build unit
-
 package merge
 
 import (
-	"os"
 	"testing"
 
+	"github.com/mongodb/openapi/tools/cli/internal/openapi"
+
 	"github.com/getkin/kin-openapi/openapi3"
 	"github.com/mongodb/openapi/tools/cli/internal/cli/flag"
 	"github.com/mongodb/openapi/tools/cli/internal/cli/validator"
-	"github.com/mongodb/openapi/tools/cli/internal/mocks"
 	"github.com/tufin/oasdiff/load"
 	"go.uber.org/mock/gomock"
 )
 
 func TestSuccessfulMerge_Run(t *testing.T) {
-	setupTest(t)
 	ctrl := gomock.NewController(t)
-	mockMergerStore := mocks.NewMockMerger(ctrl)
+	mockMergerStore := openapi.NewMockMerger(ctrl)
 
 	externalPaths := []string{"external.json"}
 	opts := &Opts{
@@ -66,10 +63,3 @@ func TestCreateBuilder(t *testing.T) {
 		[]string{flag.Base, flag.External, flag.Output},
 	)
 }
-
-func setupTest(t *testing.T) {
-	t.Helper()
-	writeToFileFunc = func(_ string, _ []byte, _ os.FileMode) error {
-		return nil
-	}
-}
diff --git a/tools/cli/internal/mocks/mock_openapi.go b/tools/cli/internal/openapi/mock_openapi.go
similarity index 93%
rename from tools/cli/internal/mocks/mock_openapi.go
rename to tools/cli/internal/openapi/mock_openapi.go
index 464e1b1..4b0dfb1 100644
--- a/tools/cli/internal/mocks/mock_openapi.go
+++ b/tools/cli/internal/openapi/mock_openapi.go
@@ -3,11 +3,11 @@
 //
 // Generated by this command:
 //
-//	mockgen -destination=../mocks/mock_openapi.go -package=mocks github.com/mongodb/openapi/tools/cli/internal/openapi Parser,Merger
+//	mockgen -destination=../openapi/mock_openapi.go -package=openapi github.com/mongodb/openapi/tools/cli/internal/openapi Parser,Merger
 //
 
-// Package mocks is a generated GoMock package.
-package mocks
+// Package openapi is a generated GoMock package.
+package openapi
 
 import (
 	reflect "reflect"
diff --git a/tools/cli/internal/openapi/openapi.go b/tools/cli/internal/openapi/openapi.go
index 555252f..07922a6 100644
--- a/tools/cli/internal/openapi/openapi.go
+++ b/tools/cli/internal/openapi/openapi.go
@@ -14,7 +14,7 @@
 
 package openapi
 
-//go:generate mockgen -destination=../mocks/mock_openapi.go -package=mocks github.com/mongodb/openapi/tools/cli/internal/openapi Parser,Merger
+//go:generate mockgen -destination=../openapi/mock_openapi.go -package=openapi github.com/mongodb/openapi/tools/cli/internal/openapi Parser,Merger
 import (
 	"log"
 

From 04bb4cd5afc85977a6780c32e125dfcd646f15f6 Mon Sep 17 00:00:00 2001
From: andreaangiolillo <andrea.angiolillo@mongodb.com>
Date: Mon, 11 Mar 2024 14:23:32 +0000
Subject: [PATCH 4/6] addressed PR comments - Part 2

---
 tools/cli/go.mod                           |  2 ++
 tools/cli/go.sum                           |  4 ++++
 tools/cli/internal/cli/merge/merge.go      | 12 +++++++-----
 tools/cli/internal/cli/merge/merge_test.go |  7 ++++---
 4 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/tools/cli/go.mod b/tools/cli/go.mod
index 6b3adad..42f46ba 100644
--- a/tools/cli/go.mod
+++ b/tools/cli/go.mod
@@ -4,6 +4,7 @@ go 1.22.1
 
 require (
 	github.com/getkin/kin-openapi v0.123.0
+	github.com/spf13/afero v1.11.0
 	github.com/spf13/cobra v1.8.0
 	github.com/stretchr/testify v1.9.0
 	github.com/tufin/oasdiff v1.10.11
@@ -25,5 +26,6 @@ require (
 	github.com/spf13/pflag v1.0.5 // indirect
 	github.com/ugorji/go/codec v1.2.11 // indirect
 	github.com/yargevad/filepathx v1.0.0 // indirect
+	golang.org/x/text v0.14.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )
diff --git a/tools/cli/go.sum b/tools/cli/go.sum
index acdc8f5..98ca60a 100644
--- a/tools/cli/go.sum
+++ b/tools/cli/go.sum
@@ -36,6 +36,8 @@ github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZN
 github.com/rogpeppe/go-internal v1.12.0 h1:exVL4IDcn6na9z1rAb56Vxr+CgyK3nn3O+epU5NdKM8=
 github.com/rogpeppe/go-internal v1.12.0/go.mod h1:E+RYuTGaKKdloAfM02xzb0FW3Paa99yedzYV+kq4uf4=
 github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
+github.com/spf13/afero v1.11.0 h1:WJQKhtpdm3v2IzqG8VMqrr6Rf3UYpEF239Jy9wNepM8=
+github.com/spf13/afero v1.11.0/go.mod h1:GH9Y3pIexgf1MTIWtNGyogA5MwRIDXGUr+hbWNoBjkY=
 github.com/spf13/cobra v1.8.0 h1:7aJaZx1B85qltLMc546zn58BxxfZdR/W22ej9CFoEf0=
 github.com/spf13/cobra v1.8.0/go.mod h1:WXLWApfZ71AjXPya3WOlMsY9yMs7YeiHhFVlvLyhcho=
 github.com/spf13/pflag v1.0.5 h1:iy+VFUOCP1a+8yFto/drg2CJ5u0yRoB7fZw3DKv/JXA=
@@ -52,6 +54,8 @@ go.uber.org/mock v0.4.0 h1:VcM4ZOtdbR4f6VXfiOpwpVJDL6lCReaZ6mw31wqh7KU=
 go.uber.org/mock v0.4.0/go.mod h1:a6FSlNadKUHUa9IP5Vyt1zh4fC7uAwxMutEAscFbkZc=
 golang.org/x/exp v0.0.0-20240119083558-1b970713d09a h1:Q8/wZp0KX97QFTc2ywcOE0YRjZPVIx+MXInMzdvQqcA=
 golang.org/x/exp v0.0.0-20240119083558-1b970713d09a/go.mod h1:idGWGoKP1toJGkd5/ig9ZLuPcZBC3ewk7SzmH0uou08=
+golang.org/x/text v0.14.0 h1:ScX5w1eTa3QqT8oi6+ziP7dTV1S2+ALU0bI+0zXKWiQ=
+golang.org/x/text v0.14.0/go.mod h1:18ZOQIKpY8NJVqYksKHtTdi31H5itFRjB5/qKTNYzSU=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EVd6muEfDQjcINNoR0C8j2r3qZ4Q=
diff --git a/tools/cli/internal/cli/merge/merge.go b/tools/cli/internal/cli/merge/merge.go
index d96ee0f..2c7750a 100644
--- a/tools/cli/internal/cli/merge/merge.go
+++ b/tools/cli/internal/cli/merge/merge.go
@@ -16,13 +16,12 @@ package merge
 
 import (
 	"fmt"
-	"log"
-	"os"
-
 	"github.com/mongodb/openapi/tools/cli/internal/cli/flag"
 	"github.com/mongodb/openapi/tools/cli/internal/cli/usage"
 	"github.com/mongodb/openapi/tools/cli/internal/openapi"
+	"github.com/spf13/afero"
 	"github.com/spf13/cobra"
+	"log"
 )
 
 const (
@@ -34,6 +33,7 @@ type Opts struct {
 	basePath      string
 	outputPath    string
 	externalPaths []string
+	fs            afero.Fs
 }
 
 func (o *Opts) Run() error {
@@ -65,7 +65,7 @@ func (o *Opts) PreRunE(_ []string) error {
 }
 
 func (o *Opts) saveFile(data []byte) error {
-	if err := os.WriteFile(o.outputPath, data, 0o600); err != nil {
+	if err := afero.WriteFile(o.fs, o.outputPath, data, 0o600); err != nil {
 		return err
 	}
 
@@ -76,7 +76,9 @@ func (o *Opts) saveFile(data []byte) error {
 // Builder builds the merge command with the following signature:
 // merge -b base-oas -e external-oas-1 -e external-oas-2
 func Builder() *cobra.Command {
-	opts := &Opts{}
+	opts := &Opts{
+		fs: afero.NewOsFs(),
+	}
 
 	cmd := &cobra.Command{
 		Use:   "merge -b base-spec [-e spec]...",
diff --git a/tools/cli/internal/cli/merge/merge_test.go b/tools/cli/internal/cli/merge/merge_test.go
index 4b9db1f..d50903d 100644
--- a/tools/cli/internal/cli/merge/merge_test.go
+++ b/tools/cli/internal/cli/merge/merge_test.go
@@ -15,13 +15,13 @@
 package merge
 
 import (
+	"github.com/spf13/afero"
 	"testing"
 
-	"github.com/mongodb/openapi/tools/cli/internal/openapi"
-
 	"github.com/getkin/kin-openapi/openapi3"
 	"github.com/mongodb/openapi/tools/cli/internal/cli/flag"
 	"github.com/mongodb/openapi/tools/cli/internal/cli/validator"
+	"github.com/mongodb/openapi/tools/cli/internal/openapi"
 	"github.com/tufin/oasdiff/load"
 	"go.uber.org/mock/gomock"
 )
@@ -29,13 +29,14 @@ import (
 func TestSuccessfulMerge_Run(t *testing.T) {
 	ctrl := gomock.NewController(t)
 	mockMergerStore := openapi.NewMockMerger(ctrl)
-
+	fs := afero.NewMemMapFs()
 	externalPaths := []string{"external.json"}
 	opts := &Opts{
 		Merger:        mockMergerStore,
 		basePath:      "base.json",
 		outputPath:    "foas.json",
 		externalPaths: externalPaths,
+		fs:            fs,
 	}
 
 	response := &load.SpecInfo{

From 11e55d99727a009769ecdb53a936a707b1ce8a7c Mon Sep 17 00:00:00 2001
From: andreaangiolillo <andrea.angiolillo@mongodb.com>
Date: Mon, 11 Mar 2024 14:25:04 +0000
Subject: [PATCH 5/6] lint

---
 tools/cli/internal/cli/merge/merge.go      | 5 +++--
 tools/cli/internal/cli/merge/merge_test.go | 2 +-
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/tools/cli/internal/cli/merge/merge.go b/tools/cli/internal/cli/merge/merge.go
index 2c7750a..4bf1abc 100644
--- a/tools/cli/internal/cli/merge/merge.go
+++ b/tools/cli/internal/cli/merge/merge.go
@@ -16,12 +16,13 @@ package merge
 
 import (
 	"fmt"
+	"log"
+
 	"github.com/mongodb/openapi/tools/cli/internal/cli/flag"
 	"github.com/mongodb/openapi/tools/cli/internal/cli/usage"
 	"github.com/mongodb/openapi/tools/cli/internal/openapi"
 	"github.com/spf13/afero"
 	"github.com/spf13/cobra"
-	"log"
 )
 
 const (
@@ -30,10 +31,10 @@ const (
 
 type Opts struct {
 	Merger        openapi.Merger
+	fs            afero.Fs
 	basePath      string
 	outputPath    string
 	externalPaths []string
-	fs            afero.Fs
 }
 
 func (o *Opts) Run() error {
diff --git a/tools/cli/internal/cli/merge/merge_test.go b/tools/cli/internal/cli/merge/merge_test.go
index d50903d..cad106f 100644
--- a/tools/cli/internal/cli/merge/merge_test.go
+++ b/tools/cli/internal/cli/merge/merge_test.go
@@ -15,13 +15,13 @@
 package merge
 
 import (
-	"github.com/spf13/afero"
 	"testing"
 
 	"github.com/getkin/kin-openapi/openapi3"
 	"github.com/mongodb/openapi/tools/cli/internal/cli/flag"
 	"github.com/mongodb/openapi/tools/cli/internal/cli/validator"
 	"github.com/mongodb/openapi/tools/cli/internal/openapi"
+	"github.com/spf13/afero"
 	"github.com/tufin/oasdiff/load"
 	"go.uber.org/mock/gomock"
 )

From 4b2fb0bd4645e6fb0413c52533cb0a5884b94159 Mon Sep 17 00:00:00 2001
From: Andrea Angiolillo <andrea.angiolillo@mongodb.com>
Date: Mon, 11 Mar 2024 14:32:38 +0000
Subject: [PATCH 6/6] Update tools/cli/Makefile

Co-authored-by: Gustavo Bazan <gus.bazan@hey.com>
---
 tools/cli/Makefile | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/cli/Makefile b/tools/cli/Makefile
index dfe6877..4453dda 100644
--- a/tools/cli/Makefile
+++ b/tools/cli/Makefile
@@ -32,8 +32,8 @@ setup: deps devtools ## Set up dev env
 
 .PHONY: fmt
 fmt: ### Format all go files with goimports and gofmt
-	find . -name "*.go" -not -path "./internal/mocks" -exec gofmt -w "{}" \;
-	find . -name "*.go" -not -path "./internal/mocks" -exec goimports -l -w "{}" \;
+	find . -name "*.go" -exec gofmt -w "{}" \;
+	find . -name "*.go" -exec goimports -l -w "{}" \;
 
 .PHONY: build
 build: